A composite lithium supplementing material, a preparation method and application thereof

Abstract

The application provides a composite lithium supplementing material and a preparation method and application thereof. The composite lithium supplementing material comprises a core and a shell layer grown in situ on the surface of the core. The core comprises a doped lithium supplementing agent, and the shell layer comprises amorphous carbon and carbon nanotubes dispersed in the amorphous carbon. The doped lithium supplementing agent contains a transition metal element. The carbon nanotubes and amorphous carbon grown and coated on the surface of the core material can isolate the influence of external environmental factors on the core material, so that the composite lithium supplementing material has the characteristics of being stable during storage and battery process. In addition, the carbon nanotubes have regular crystal form and good conductivity, which can further improve the conductivity of the composite lithium supplementing material, thereby improving the battery capacity, reducing the amount of conductive agent in the electrode sheet, reducing the battery internal resistance, and prolonging the cycle life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a composite lithium supplementing material and a preparation method and application thereof. BACKGROUND

[0002] With the development of new energy industry, the market has higher and higher requirements for the energy density of lithium batteries, and it is imperative to develop lithium batteries with large capacity, long service life and high safety performance. During the first charge and discharge process of lithium batteries, the formation of SEI film on the surface of electrode plate will cause irreversible loss of active Li + , reduce the total amount of active Li + , and the capacity and performance of electrode active material cannot be fully utilized, resulting in loss of battery capacity and shortening of battery service life. At present, the industry usually supplements lithium in the positive and negative electrode active materials to solve the above problems, and the positive electrode lithium supplementing is safer and simpler in process than the negative electrode lithium supplementing. However, the positive electrode lithium supplementing material has high residual alkali value and poor stability, and is easily reacted with moisture and CO2 in the air. The industry generally improves the stability of the positive electrode lithium supplementing material by doping or setting a coating layer, but the improvement effect is limited. SUMMARY

[0003] Therefore, the present application provides a composite lithium supplementing material and a preparation method and application thereof. The composite lithium supplementing material has the characteristics of stable existence during storage and battery process. In addition, the carbon nanotubes in the shell layer have regular crystal form and good conductivity, which can further improve the conductivity of the composite lithium supplementing material.

[0004] The first aspect of the present application provides a composite lithium supplementing material, which comprises a core and a shell layer grown in situ on the surface of the core. The core comprises a doped lithium supplementing agent, and the shell layer comprises amorphous carbon and carbon nanotubes dispersed in the amorphous carbon. The doped lithium supplementing agent contains a transition metal element.

[0005] The carbon nanotubes and amorphous carbon grown and coated on the surface of the core material can isolate the influence of external environmental factors on the core material, so that the composite lithium supplementing material has the characteristics of stable existence during storage and battery process. In addition, the carbon nanotubes have regular crystal form and good conductivity, which can further improve the conductivity of the composite lithium supplementing material, thereby improving the battery capacity, reducing the amount of conductive agent in the electrode plate, reducing the internal resistance of the battery, and prolonging the cycle life of the battery.

[0006] The second aspect of the present application provides a preparation method of a composite lithium supplementing material, comprising the following steps:

[0007] (1) mixing a lithium supplementing agent source and a doping source to prepare a doped lithium supplementing agent precursor;

[0008] (2) mixing the doped lithium supplement precursor with an organic carbon source, and calcining under an inert atmosphere to grow carbon nanotubes and amorphous carbon, to obtain a composite lithium supplement material; wherein the composite lithium supplement material comprises a core and a shell, the core comprises a doped lithium supplement, and the shell comprises amorphous carbon and carbon nanotubes dispersed in the amorphous carbon, and the doped lithium supplement contains a transition metal element.

[0009] The third aspect of the present application provides a positive electrode composite material, which comprises the composite lithium supplement material provided in the first aspect of the present application or prepared by the preparation method provided in the second aspect of the present application.

[0010] The positive electrode composite material has good lithium supplement performance and good processing performance, and can be used to provide a battery with high initial charge-discharge coulomb efficiency and long cycle service life.

[0011] The fourth aspect of the present application provides a positive electrode tab, which comprises the positive electrode composite material provided in the third aspect of the present application.

[0012] The positive electrode tab has good lithium supplement effect, and can be used to provide a battery with high initial charge-discharge coulomb efficiency and long cycle service life.

[0013] The fifth aspect of the present application provides a battery, which comprises the positive electrode tab provided in the fourth aspect of the present application.

[0014] The battery has high initial charge-discharge coulomb efficiency and long cycle service life. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A structure schematic diagram of the composite lithium supplement material provided in an embodiment of the present application;

[0016] Figure 2A And Figure 2B A scanning electron microscopy (SEM) photograph of the composite lithium supplement material prepared in Embodiment 1 of the present application under different magnifications. DETAILED DESCRIPTION

[0017] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings.

[0018] Please refer to Figure 1 The composite lithium supplement material 100 comprises a core 10 and a shell 11 grown in situ on the surface of the core 10, the core 10 comprises a doped lithium supplement, and the shell 11 comprises amorphous carbon 110 and carbon nanotubes 111 dispersed in the amorphous carbon 110; wherein the doped lithium supplement contains a transition metal element.

[0019] The transition metal element in the doped lithium supplementing agent can catalyze carbon atoms in the organic carbon source to generate carbon nanotubes 111 in situ on the surface of the doped lithium supplementing agent and continuously precipitate amorphous carbon 110, both of which are coated on the surface of the doped lithium supplementing agent to form a composite lithium supplementing material 100 with a core-shell structure. The carbon nanotubes 111 have high crystalline regularity and good electrical conductivity, and the in-situ grown carbon nanotubes 111 inherit the dispersion position of the doped elements in the doped lithium supplementing agent, which can be uniformly dispersed in the composite lithium supplementing material 100, thereby avoiding the phenomenon of carbon nanotube agglomeration that is prone to occur in traditional coating methods, and more conducive to the transmission of electrons, thereby further improving the electrical conductivity of the composite lithium supplementing material 100.

[0020] In addition, the shell layer 11 directly grown on the surface of the inner core 10 has good interfacial bonding force with the inner core 10, which can improve the structural stability of the composite lithium supplementing material 100. Moreover, the carbon nanotubes 111 are not hydrophilic and not oleophilic, and their water-blocking performance is better than that of the amorphous carbon 110, and the dense shell layer 11 formed by the two can effectively prevent the doped lithium supplementing agent in the inner core 10 from reacting with water and CO2 and other components in the air, thereby significantly improving the storage stability of the composite lithium supplementing material 100 itself in the air environment, and effectively avoiding the phenomenon that the composite lithium supplementing material 100 is prone to react with water and other components during the preparation of the positive electrode slurry, causing the positive electrode slurry to gel, not easy to stir, and not easy to be dosed. Furthermore, the doped lithium supplementing agent has a high specific capacity, and the electrostatic interaction between the doped elements can further improve the structural stability of the inner core 10. Therefore, the composite lithium supplementing material 100 has the characteristics of high specific capacity, good environmental stability, structural stability, and good electrical conductivity, which is conducive to promoting the capacity and performance of the positive active material, thereby improving the first charge-discharge coulombic efficiency, energy density, and cycle capacity retention rate of the lithium battery, and prolonging the service life of the battery.

[0021] In the present application, the above-mentioned carbon nanotubes 111 can be multi-walled carbon nanotubes or single-walled carbon nanotubes.

[0022] In some embodiments of the present application, the transition metal element in the doped lithium supplementing agent includes but is not limited to at least one of Fe, Co, Ni, Mn, Mo, and Cu.

[0023] In the present application, the undoped lithium supplementing agent body can contain a transition metal element or can not contain a transition metal element. In order to better distinguish, the transition metal element in the lithium supplementing agent body is denoted as transition metal element A, and whether the body contains the transition metal element A or not, it will be doped, and the doped element can be a transition metal element, thereby obtaining a doped lithium supplementing agent containing a transition metal element.

[0024] In some embodiments of the present application, in the above doped lithium supplementing agent, the doped element includes, but is not limited to, at least one of Fe, Co, Ni, Mn, Mo and Cu. At this time, the undoped lithium supplementing agent can or can not contain transition metal element A. In the present application, the above doped element can be doped in the lithium supplementing agent in the form of a single element or in the form of a metal oxide. Those skilled in the art can select according to actual production needs and the catalytic effect of the doped element. The above doped element also belongs to a transition metal element, and in order to facilitate the distinction, the doped transition metal element is denoted as transition metal element M. The above transition metal element A and transition metal element M can be the same or different, and those skilled in the art can select according to actual production needs. In the preparation process of the composite lithium supplementing material, the single element or oxide of the above doped transition metal element M is a high-quality active center, which can catalyze the cracking of the organic carbon source and the rearrangement of carbon atoms to generate carbon nanotubes and amorphous carbon, so that the composite lithium supplementing material provided in the embodiments of the present application can be successfully prepared. In addition, the doping of the above transition metal element M can improve the specific capacity of the lithium supplementing agent.

[0025] In some embodiments of the present application, in the above doped lithium supplementing agent, the mole percentage of the above doped element in the core 10 is in the range of 1% to 50%. Exemplarily, the mole percentage of the above doped element in the core 10 can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. In some specific embodiments, the mole percentage of the above doped element in the core 10 is in the range of 1% to 10%. Controlling the content of the doped element in the above range is beneficial on the one hand to ensure that the grown shell 11 has a suitable thickness and density, so that the composite lithium supplementing material 100 has good environmental stability and ion transmission rate, and on the other hand, the presence of an appropriate amount of doped element is also beneficial to improve the specific capacity and structural stability of the composite lithium supplementing material 100.

[0026] In some embodiments of the present application, in the above doped lithium supplementing agent, a second element is doped, and the above second element includes Al and / or Mg. The second element can be doped in the lithium supplementing agent in the form of a single element and / or an oxide. At this time, the undoped lithium supplementing agent needs to contain the above transition metal element A, and the transition metal element A in the phase of the lithium supplementing agent on the surface of the core 10 needs to be reduced in the preparation process of the composite lithium supplementing material 100. Al and / or Mg can improve the catalytic activity of the transition metal single element or oxide, so that the doped Al and / or Mg and the reduced transition metal element single element can catalyze the growth of carbon nanotubes and amorphous carbon, so that the composite lithium supplementing material 100 can be successfully prepared. At this time, the mole percentage of the above second element in the core 10 is 1% to 25%. An appropriate ratio of the two is beneficial to promote the efficient growth of carbon nanotubes.

[0027] In some embodiments of the present application, the doped lithium supplementing agent can be doped with both transition metal element M and a second element. In this case, the presence of transition metal element A in the undoped lithium supplementing agent is not limited. The second element can cooperate with the doped transition metal element M to form a binary or even ternary catalyst to efficiently catalyze the growth of carbon nanotubes. For example, the doped transition metal element M and the second element can form a Co / MgO catalyst, a Fe-based catalyst (Fe-Mo / MgO), a Ni-based catalyst (Ni-Mo / MgO), and the like.

[0028] In some embodiments of the present application, the mass percentage of the carbon nanotubes 111 in the shell layer 11 is in the range of 0.1% to 10%. For example, the mass percentage of the carbon nanotubes 111 in the shell layer 11 can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and the like. In some specific embodiments, the mass percentage of the carbon nanotubes 111 in the shell layer 11 is in the range of 0.1% to 5%. An appropriate amount of carbon nanotubes can improve the electrical conductivity and environmental stability of the composite lithium supplementing material 100, and an appropriate amount of amorphous carbon is conducive to ensuring the compactness of the shell layer 11, so that the composite lithium supplementing material 100 has good environmental stability and better electrical conductivity.

[0029] In some embodiments of the present application, at least part of the carbon nanotubes 111 are in contact with the core 10. In the preparation process of the composite lithium supplementing material 100, most of the active centers are still doped in the doped lithium supplementing agent, and the in-situ grown carbon nanotubes 111 inherit the dispersion position of the active centers, so that most of the carbon nanotubes 111 grow from the core and extend in the direction of the shell layer 11. The carbon nanotubes 111 can grow from the inside of the core or from the interface between the core 10 and the shell layer 11. That is, the carbon nanotubes 111 are interspersed in the amorphous carbon and in contact with the core 10. In this case, the interfacial bonding force between the shell layer 11 and the core 10 can be significantly improved, thereby significantly improving the structural stability of the composite lithium supplementing material 100.

[0030] In some embodiments of the present application, part of the carbon nanotubes 111 are not in contact with the core 10. In the preparation process of the composite lithium supplementing material 100, under the action of high temperature, a small amount of doping elements can migrate into the amorphous carbon 110 or be doped in the newly generated carbon nanotubes 111, and this part of the doping elements can catalyze the growth of the carbon nanotubes 111 directly in the shell layer, so that part of the carbon nanotubes 111 are not in contact with the core 10.

[0031] In some embodiments of the present application, at least part of the carbon nanotubes 111 form a three-dimensional conductive network on the surface of the core 10. When the content of the carbon nanotubes 111 is high, a large number of carbon nanotubes 111 are arranged in a staggered manner, and a three-dimensional conductive network can be formed on the surface of the core 10, which can further improve the conductivity of the composite lithium supplementing material 100.

[0032] In some embodiments of the present application, the diameter of the carbon nanotubes 111 is in the range of 5 nm to 100 nm. For example, the diameter of the carbon nanotubes 111 can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc. In some specific embodiments, the diameter of the carbon nanotubes 111 is in the range of 5 nm to 20 nm. Further preferably, the diameter of the carbon nanotubes 111 can be 9 nm to 11 nm. The conductivity of the carbon nanotubes is related to the size of the diameter thereof, and the carbon nanotubes with a suitable diameter have better conductivity, which is more conducive to the performance of the composite lithium supplementing material 100.

[0033] In some embodiments of the present application, the wall thickness of the carbon nanotubes 111 is in the range of 0.05 nm to 2 nm. For example, the wall thickness of the carbon nanotubes 111 can be 0.05 nm, 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 2 nm, etc. In some specific embodiments, the wall thickness of the carbon nanotubes 111 is in the range of 0.5 nm to 1.5 nm.

[0034] In some embodiments of the present application, the length of the carbon nanotubes 111 is in the range of 3 μm to 50 μm. For example, the length of the carbon nanotubes can be 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc. In some specific embodiments, the length of the carbon nanotubes 111 is in the range of 5 μm to 30 μm. At this time, it is conducive to the carbon nanotubes to form a conductive network, thereby further improving the conductivity of the composite lithium supplementing material 100.

[0035] In some embodiments of the present application, the aspect ratio of the carbon nanotubes 111 is in the range of 50 to 10,000. In some specific embodiments, the aspect ratio of the carbon nanotubes 111 is in the range of 50 to 5,000. A high aspect ratio can improve the conductivity of the carbon nanotubes, thereby being conducive to improving the conductivity of the composite lithium supplementing material.

[0036] In some embodiments of the present application, the average thickness of the shell layer 11 is in the range of 3 nm-100 nm. Exemplarily, the average thickness of the shell layer 11 can be 3 nm-8 nm, 10 nm-15 nm, 15 nm-20 nm, 20 nm-30 nm, 30 nm-40 nm, 40 nm-50 nm, 50 nm-60 nm, 60 nm-70 nm, 70 nm-80 nm, 80 nm-90 nm, 90 nm-100 nm, 3 nm, 5 nm, 6 nm, 7 nm, 8 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc. Controlling the thickness of the shell layer 11 in a suitable range is conducive to ensuring the stability of the composite lithium supplementing material 100 in the air and during the preparation of the battery, and conducive to controlling the path of ion transmission to be short, thereby facilitating the realization of efficient lithium supplementing.

[0037] In some embodiments of the present application, the mass percentage of the shell layer 11 in the composite lithium supplementing material 100 is 1.0%-5.5%. Exemplarily, the mass percentage of the shell layer 11 in the composite lithium supplementing material 100 can be 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, etc. Controlling the mass percentage of the shell layer 11 in the above range can further control the thickness of the shell layer 11, thereby facilitating the environmental stability and electrical conductivity, and preventing the over-thick shell layer from reducing the lithium supplementing capacity of the composite lithium supplementing material and its conductivity to lithium ions during the charging process of the battery, thereby facilitating the realization of efficient lithium supplementing.

[0038] In some embodiments of the present application, the diameter of the core 10 is in the range of 0.05 μm-100 μm. Exemplarily, the diameter of the core 10 can be 0.05 μm-3 μm, 5 μm-10 μm, 10 μm-20 μm, 25 μm-30 μm, 30 μm-40 μm, 40 μm-50 μm, 50 μm-60 μm, 60 μm-70 μm, 70 μm-80 μm, 80 μm-100 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 80 μm, 90 μm, etc. In some specific embodiments, the diameter of the core 10 is in the range of 0.05 μm-30 μm. Controlling the diameter of the core 10 in a suitable range can effectively facilitate the size of the composite lithium supplementing material 100 to be in a suitable range, thereby facilitating the performance of the lithium supplementing property.

[0039] In some embodiments of the present application, the above-mentioned doped transition metal elements can also react with organic carbon sources to form carbides during the preparation of the composite lithium supplement material 100, which not only improves the binding stability and tightness of the shell layer 11 and the inner core 10, but also the newly formed carbides can further act as active catalytic centers to better promote the growth of amorphous carbon and carbon nanotubes, and improve the coating degree and quality of amorphous carbon and carbon nanotubes on the surface of the inner core 10.

[0040] In some embodiments of the present application, the composite lithium supplement material 100 also has an encapsulation layer coated on the outer surface of the shell layer 11. The encapsulation layer includes but is not limited to at least one of the isolation sub-packaging layer, the ion conductor encapsulation layer, and the electronic conductor encapsulation layer. These encapsulation layers can effectively improve the electronic and ionic conduction performance of the lithium supplement agent in the inner core 10, improve the release rate of active lithium during charging, and also play a certain role in isolating moisture to improve the stability of the composite lithium supplement material 100 and achieve stable lithium supplement effect. In addition, it can further improve the stability, uniformity of dispersion, and good processing performance of the composite lithium supplement material 100 in the electrode active slurry and active layer. Specifically, the isolation encapsulation layer further protects the composite lithium supplement material, further reducing the risk of contact between the inner core and water and CO2 in the environment; the electronic conductor encapsulation layer can enhance the electronic conductivity of the shell layer, thereby enhancing the electronic conductivity of the composite lithium supplement material 100 and reducing the internal impedance of the electrode; the ion conductor encapsulation layer can enhance the ionic conductivity of the composite lithium supplement material 100, thereby enhancing the ionic conductivity of the composite lithium supplement material 100, which is conducive to the outward transport of lithium ions in the inner core.

[0041] In some specific embodiments, the encapsulation layer can be a separate isolation encapsulation layer, which fully coats the inner core 10 and the shell layer 11 to play a protective role and further improve the stability of the inner core 10. It can also be a composite laminated structure of the isolation encapsulation layer and the electronic conductor encapsulation layer, and the preferred structure is that the isolation encapsulation layer is coated on the outer surface of the shell layer, and the electronic conductor encapsulation layer is coated on the outer surface of the isolation encapsulation layer. It can also be a composite laminated structure of the isolation encapsulation layer and the ion conductor encapsulation layer, and the preferred structure is that the isolation encapsulation layer is coated on the outer surface of the shell layer, and the ion conductor encapsulation layer is coated on the outer surface of the isolation encapsulation layer. It can also be a composite laminated structure of the isolation encapsulation layer, the electronic conductor encapsulation layer, and the ion conductor encapsulation layer. The preferred structure is that the isolation encapsulation layer is coated on the outer surface of the shell layer, the ion conductor encapsulation layer is coated on the outer surface of the isolation encapsulation layer, and the electronic conductor encapsulation layer is coated on the outer surface of the ion conductor encapsulation layer; or, the isolation encapsulation layer is coated on the outer surface of the shell layer, the electronic conductor encapsulation layer is coated on the outer surface of the isolation encapsulation layer, and the ion conductor encapsulation layer is coated on the outer surface of the electronic conductor encapsulation layer.

[0042] In some embodiments, the material of the isolation encapsulation layer includes, but is not limited to, at least one of ceramics, polymers, and carbon materials. In some embodiments, the ceramics include, but are not limited to, at least one of Al₂O₃, SiO₂, boehmite, Si₃N₄, SiC, and BN. In some embodiments, the polymers include, but are not limited to, [C₆H₇O₆Na]. n Organic polymers with the structure [C6H7O2(OH)2OCH2COONa] n Organic polymers with the structure [C3H4O2] n Organic polymers with the structure [C3H3O2M] a ] n Organic polymers with the structure [C3H3N] n It is an organic polymer with a structure containing -[CH2-CF2]. n At least one of the following: an organic polymer with a -[NHCO]- structure, an organic polymer containing an imide ring -[CO-N-CO]- structure on its main chain, and polyvinylpyrrolidone, wherein M a The polymer is an alkali metal element. Specifically, the polymer includes, but is not limited to, at least one of polyvinylidene fluoride, sodium alginate, sodium carboxymethyl cellulose, polyacrylic acid, polyacrylate, polyacrylonitrile, polyamide, polyimide, polyvinylpyrrolidone, polyethylene oxide (PEO), polypyrrole (PPy), polytetrafluoroethylene (PTFE), and polyurethane (PU). Further, the polymer includes, but is not limited to, at least one of sodium carboxymethyl cellulose and polyacrylic acid. Sodium carboxymethyl cellulose and polyacrylic acid are two-dimensional planar polymers with good adhesive properties, capable of effectively coating the doped lithium supplement core, thereby preventing the core material from contacting air and improving the stability of the composite lithium supplement material 100. In some embodiments, the molecular weight of the polymer is greater than or equal to 100,000. Exemplarily, the molecular weight of the polymer can be 100,000, 150,000, 200,000, 300,000, 500,000, 1,000,000, etc. The higher the molecular weight of the polymer, the higher the density and structural strength of the polymer layer, which is more conducive to protecting the core material. In some specific embodiments, the carbon material includes, but is not limited to, at least one of graphene, carbon nanotubes, amorphous carbon, graphite, and carbon black.

[0043] In some specific embodiments, the thickness of the isolation encapsulation layer is in the range of 5nm-200nm. More preferably, the thickness of the isolation encapsulation layer is in the range of 5nm-50nm. By adjusting the material and thickness of the isolation encapsulation layer, the contact between water and CO2 and the doped lithium supplement in the core can be further improved, thereby enhancing the stability of the composite lithium supplement material 100.

[0044] In some embodiments, the material of the electronic conductor encapsulation layer includes, but is not limited to, at least one of carbon materials, conductive polymers, and conductive oxides. In some embodiments, the carbon materials include, but are not limited to, at least one of mesoporous carbon, carbon nanotubes, graphite, carbon black, and graphene, the conductive polymers include, but are not limited to, the conductive polymers contained in the isolation encapsulation layer as described above, and the conductive oxides include, but are not limited to, at least one of In2O3, ZnO, and SnO2.

[0045] In some embodiments, the thickness of the electronic conductor encapsulation layer is in the range of 5 nm-200 nm; further preferably, the thickness of the electronic conductor encapsulation layer is in the range of 5 nm-50 nm. By adjusting the thickness of the electronic conductor encapsulation layer, the electronic conductivity of the composite lithium supplementing material 100 can be further improved.

[0046] In some embodiments, the material of the ion conductor encapsulation layer includes, but is not limited to, at least one of perovskite type, NASICON type, garnet type, or polymer type solid-state electrolyte. In some embodiments, the perovskite type includes, but is not limited to, at least one of Li 3x La 2 / 3-x TiO3(LLTO), specifically Li 0.5 La 0.5 TiO3, Li 0.33 La 0.57 TiO3, Li 0.29 La 0.57 TiO3, Li 0.33 Ba 0.25 La 0.39 TiO3, (Li 0.33 La 0.56 ) 1.005 Ti 0.99 Al 0.01 O3and Li 0.5 La 0.5 Ti 0.95 Zr 0.05 O3. The NASICON type includes, but is not limited to, at least one of Li 1.4 Al 0.4 Ti 1.6 (PO4)3(LATP). The garnet type includes, but is not limited to, Li7La3Zr2O 12 (LLZO, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 and Li 6.5 La3Zr 1.5 Ta 0.5 O 12At least one of the following; polymer-type solid electrolytes include, but are not limited to, at least one of PEO / PPO / PVDF containing dissolved lithium salts.

[0047] In some specific embodiments, the thickness of the ion conductor encapsulation layer is in the range of 5 nm to 200 nm. More preferably, the thickness of the ion conductor encapsulation layer is in the range of 5 nm to 50 nm. By adjusting the thickness and material of the ion conductor encapsulation layer, the ionic conductivity of the composite lithium replenishment material 100 can be further improved.

[0048] Accordingly, this application also provides a method for preparing a composite lithium replenishing material, which can be used to prepare the composite lithium replenishing material 100 provided in this application. The preparation method includes the following steps:

[0049] (1) Mix the lithium replenishing agent source with the doping source to prepare a doped lithium replenishing agent precursor;

[0050] (2) The above-mentioned doped lithium replenishing agent precursor is mixed with an organic carbon source and calcined under an inert atmosphere to grow carbon nanotubes and amorphous carbon to obtain a composite lithium replenishing material; wherein the above-mentioned composite lithium replenishing material includes a core and a shell, the above-mentioned core includes a doped lithium replenishing agent, the above-mentioned shell includes amorphous carbon and carbon nanotubes dispersed in the amorphous carbon, and the above-mentioned doped lithium replenishing agent contains a transition metal element.

[0051] Carbon atoms in organic carbon sources can undergo carbon rearrangement reactions on the surface of doped lithium supplements, allowing carbon nanotubes and amorphous carbon to grow on the surface of the core material, thus forming a composite lithium supplement material with a core-shell structure.

[0052] This preparation method is simple and suitable for large-scale industrial production.

[0053] In this application, the inert atmosphere can be at least one of nitrogen, helium, and argon.

[0054] In some embodiments of this application, the calcination conditions in step (2) are: 500℃-750℃ under nitrogen atmosphere, held for 30min-90min. The specific calcination temperature and holding time can be determined according to the actual situation, and the suitable temperature for the catalytic generation of carbon nanotubes varies for different elements. Suitable calcination conditions are beneficial to the growth of carbon nanotubes and amorphous carbon, thereby helping to ensure good performance of the composite lithium supplementation material.

[0055] In some embodiments of this application, the doping source includes at least one of the following: nitrate, sulfate, carbonate, hydroxide, and ammonium salt of the doping element. The doping element includes the aforementioned transition metal element M, which includes, but is not limited to, at least one of Fe, Co, Ni, Mn, Mo, and Cu.

[0056] In some embodiments of the present application, the doping source includes at least one of nitrate, sulfate, carbonate, hydroxide and ammonium salt of the doping element. The doping element includes, but is not limited to, Al and / or Mg. It is noted that if the transition metal element A is present in the lithium supplement source, the doping source can only be at least one of nitrate, sulfate, carbonate, hydroxide and ammonium salt of Al and / or Mg. If the transition metal element A is not present in the lithium supplement source, the doping source must also include at least one of nitrate, sulfate, carbonate, hydroxide and ammonium salt of the transition metal element M.

[0057] Each of the above-mentioned doping sources is easy to be reduced to an element or oxidized to an oxide, and other elements are removed in the form of gas, and are not easy to remain.

[0058] In some embodiments of the present application, the organic carbon source includes, but is not limited to, at least one of alcohol, aldehyde, alkane, alkene, alkyne and benzene. Exemplarily, the organic carbon source can be polypropylene, polyethylene, ethanol, benzene, toluene and polyaniline, etc.

[0059] In the present application, the organic carbon source can be in a gaseous state or a liquid state.

[0060] In the present application, the lithium supplement source can be a material known to those skilled in the art. Exemplarily, the lithium supplement source includes, but is not limited to, Li4FeO5, lithium cobaltate, lithium aluminates, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium phosphate oxide, fluorinated lithium vanadium phosphate, lithium titanate, lithium high-nickel, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, etc.

[0061] In some embodiments of the present application, after step (2), step (3) is further included: forming an encapsulation layer on the surface of the shell layer. The encapsulation layer includes, but is not limited to, at least one of a separation encapsulation layer, an ion conductor encapsulation layer and an electron conductor encapsulation layer. The preparation method of the encapsulation layer includes, but is not limited to, chemical deposition, magnetron sputtering, atomic layer deposition, etc.

[0062] In some specific embodiments, when the material of the encapsulation layer is a ceramic layer, the step of preparing the ceramic encapsulation layer can adopt a magnetron sputtering method to sputter and deposit a ceramic target on the surface of the shell layer to form a ceramic encapsulation layer, wherein the conditions of magnetron sputtering are adjusted according to the specific properties of the target material.

[0063] In some embodiments, when the material of the encapsulation layer is a high polymer layer, the step of forming the high polymer isolation encapsulation layer can be: dispersing the composite lithium supplementing material prepared in step (2) in a solution containing a high polymer, and then vacuum drying to form a dense polymer encapsulation layer on the surface of the shell. The solvent of the solution is a solvent capable of uniformly dispersing or dissolving the high polymer, such as one or more of N-methyl pyrrolidone, methanol, ethanol, isopropanol, acetone, tetrahydrofuran, and diethyl ether.

[0064] In some embodiments, when the material of the encapsulation layer is a carbon material layer, the method of forming the carbon material isolation encapsulation layer includes the following steps: dispersing the composite lithium supplementing material prepared in step (2) in a solution containing a carbon source, and after drying treatment, performing carbonization treatment to form a dense carbon encapsulation layer on the surface of the shell. The carbon source can be, but is not limited to, PEO, and can also be other carbon sources. As long as it can form a carbon-coated source layer on the composite lithium supplementing material. Specifically, the carbon-coated lithium supplementing material can be mixed with PEO uniformly, and treated at 300°C to make the molten PEO uniformly coat the surface of the shell. The coated material is sintered at 600°C for 6 hours in an inert atmosphere.

[0065] The application also provides a positive electrode composite material, which includes the composite lithium supplementing material provided by the application or the composite lithium supplementing material prepared by the preparation method provided by the application.

[0066] The positive electrode composite material has good lithium supplementing performance and good processing performance, and can be used to provide a battery with high initial charge-discharge coulomb efficiency and long cycle service life.

[0067] In some embodiments of the application, the positive electrode composite material further includes a positive electrode active material, and the mass percentage of the composite lithium supplementing material in the positive electrode composite material is in the range of 0.1% to 10%. For example, the mass percentage of the composite lithium supplementing material in the positive electrode composite material can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. The content of the composite lithium supplementing material can be determined according to the actual lithium supplementing demand of the battery. Controlling the content of the composite lithium supplementing material in the above range can effectively compensate for the loss of active Li + in the first charging process of the battery, improve the initial charge-discharge coulomb efficiency of the battery, and help to improve the energy density and capacity retention rate of the battery.

[0068] In the present application, the positive electrode active material is a material known to those skilled in the art. Specifically, the positive electrode active material includes, but is not limited to, at least one of a phosphate positive electrode active material, a ternary positive electrode active material, and a lithium transition metal oxide. Exemplarily, the positive electrode active material can be lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium phosphate oxide, fluorinated lithium vanadium phosphate, lithium titanate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, etc.

[0069] The present application also provides a positive electrode tab with the positive electrode composite provided by the present application. The positive electrode tab has good lithium supplement effect and can be used to provide a battery with high first charge-discharge coulomb efficiency and long cycle service life.

[0070] In the present application, the positive electrode tab includes a current collector and a positive electrode active material layer arranged on at least one side surface of the current collector.

[0071] In some embodiments of the present application, the positive electrode current collector includes, but is not limited to, any one of a copper foil and an aluminum foil.

[0072] In some embodiments of the present application, the positive electrode active layer can further include a conductive agent, an adhesive, etc. The conductive agent and the adhesive are materials known to those skilled in the art, and suitable materials can be selected according to actual application requirements.

[0073] In some embodiments of the present application, the mass percentage of the binder in the positive electrode active layer is in the range of 2%-4%. Exemplarily, the mass percentage of the binder in the positive electrode active layer can be 2%, 3%, 4%, etc. Exemplarily, the binder includes at least one of polyvinylidene chloride, soluble polytetrafluoroethylene, butadiene rubber, hydroxypropyl methyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

[0074] In some embodiments of the present application, the mass percentage of the conductive agent in the positive electrode active layer is in the range of 3%-5%. Exemplarily, the mass percentage of the conductive agent in the positive electrode active layer can be 3%, 4%, 5%, etc. Exemplarily, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotube.

[0075] In the present application, the preparation process of the positive electrode tab can include the following steps:

[0076] Mixing the positive electrode active material, the composite lithium supplement material, the conductive agent, the binder, and the solvent to obtain a positive electrode slurry;

[0077] Coating the positive electrode slurry on the current collector, and preparing the positive electrode tab through drying, rolling, die cutting, etc.

[0078] The application also provides a battery with the positive electrode sheet provided by the application. The battery has higher initial charge-discharge coulomb efficiency and longer cycle service life.

[0079] The technical solutions of the application will be described in detail below with specific examples.

[0080] Example 1

[0081] (1) LiOH and CS2 (CS2 is used to provide anions combined with Li + The doped lithium supplement precursor is obtained by uniformly mechanically crushing and stirring LiOH, CS2 and Cu(NO3)2 in a molar ratio of 4:1:0.5, sintering at 800 DEG C for 10 hours under a nitrogen atmosphere, crushing, and sieving.

[0082] (2) The benzene and the doped lithium supplement precursor are uniformly mixed, and then sintered at 700 DEG C for 1.5 hours under a nitrogen atmosphere in a muffle furnace to obtain the composite lithium supplement material provided by the application.

[0083] The average thickness of the shell layer is 6 nm, and the average particle size of the inner core is 10 μm. The mass percentage of the shell layer is 1.75%, and the mass percentage of the carbon nanotubes in the shell layer is 0.15%. The obtained carbon nanotubes have a tube diameter in the range of 30-50 nm and a length in the range of 3-8 μm. The chemical formula of the inner core can be expressed as Li2S·0.5CuO. Cu is a doped element, and CuO can catalyze the growth of carbon nanotubes and amorphous carbon during the preparation of the composite lithium supplement material, and Li2S provides Li + .

[0084] Example 2

[0085] (1) Li2O and Ni(OH)2 are mechanically crushed and uniformly stirred in a molar ratio of 1:1, and then sintered at 700 DEG C for 10 hours under a nitrogen atmosphere, crushed, and sieved to obtain a lithium supplement source Li2NiO2.

[0086] (2) The lithium supplement source Li2NiO2 and the doping source (NH4)2MoO4 are uniformly mixed in a ratio of 1:0.05, and then sintered at 450 DEG C for 2 hours under a nitrogen and hydrogen atmosphere, crushed, and sieved to obtain a doped lithium supplement precursor.

[0087] (3) The ethanol and the doped lithium supplement precursor are uniformly mixed, and then reacted at 650 DEG C for 0.5 hours under a nitrogen atmosphere in a tube furnace to obtain the composite lithium supplement material provided by the application.

[0088] The average thickness of the shell layer is 5 nm, and the average particle size of the core is 3 μm. The mass percentage of the shell layer is 1.98%, and the mass percentage of the carbon nanotubes in the shell layer is 0.5%. The carbon nanotubes obtained have a tube diameter in the range of 20-30 nm and a length in the range of 5-10 μm. The chemical formula of the core can be expressed as Li2NiO2·0.05Mo, wherein Mo is doped in Li2NiO2 in the form of an element, and Mo catalyzes the growth of carbon nanotubes and amorphous carbon, and Li2NiO2 provides Li as a lithium supplement + .

[0089] Example 3

[0090] (1) Li2CO3 and Fe(OH)3 were mechanically crushed in a molar ratio of 2.6:1, uniformly stirred, and sintered at 850°C for 12 h under an argon atmosphere, crushed, and sieved to obtain a lithium supplement source-Li5FeO4.

[0091] (2) The lithium supplement source-Li5FeO4 and the doping source-Al(NO3)3 were uniformly mixed in a ratio of 1:1, sintered at 550°C for 3 h in a mixed atmosphere of hydrogen and nitrogen, crushed, and sieved to obtain a doped lithium supplement precursor, wherein the hydrogen reduced the Fe element on the surface of the lithium supplement source.

[0092] (3) The polypropylene waste plastic was first crushed, uniformly mixed with the doped lithium supplement precursor, and placed in a box furnace to react at 600°C for 1 h under a nitrogen atmosphere to obtain the composite lithium supplement material provided in the application.

[0093] The average thickness of the shell layer is 3 nm, and the average particle size of the core is 4 μm. The mass percentage of the shell layer is 1.23%, and the mass percentage of the carbon nanotubes in the shell layer is 0.4%. The carbon nanotubes obtained have a tube diameter in the range of 10-20 nm and a length in the range of 10-15 μm. The chemical formula of the doped lithium supplement can be expressed as Li5FeO4·0.1Fe·Al2O3, wherein the reduced Fe element is located on the surface of the core material and catalyzes the growth of carbon nanotubes and amorphous carbon together with the doped Al2O3, and Li5FeO4 in the core material provides Li as a lithium supplement + .

[0094] Example 4

[0095] (1) Li2CO3 and Fe(OH)3 were mechanically crushed in a molar ratio of 2.5:1, uniformly stirred, and sintered at 700°C for 10 h under a nitrogen atmosphere, crushed, and sieved to obtain a lithium supplement source-Li5FeO4.

[0096] (2) Mix the lithium supplement source-Li5FeO4 and the doping source-(NH4)2MoO4 and Al(NO3)3 in a proportion of 1:0.05:1, and then sinter at 450°C for 2h under an atmosphere, crush, sieve, and obtain a doped lithium supplement agent precursor.

[0097] (3) Mix ethanol with the doped lithium supplement agent precursor, and then place in a tube furnace and react at 650°C for 0.5h under a nitrogen atmosphere to obtain the composite lithium supplement material provided in the embodiments.

[0098] The average thickness of the shell layer is 3nm, and the average particle size of the inner core is 2μm. The mass percentage of the shell layer is 1.48%, and the mass percentage of the carbon nanotubes in the shell layer is 0.2%. The carbon nanotubes obtained have a tube diameter in the range of 25nm-40nm and a length in the range of 5μm-10μm. The chemical formula of the inner core can be expressed as Li5FeO4·0.05Mo·Al2O3. The Mo element and Al2O3 are doped in Li5FeO4, and Mo and Al2O3 synergistically catalyze the growth of carbon nanotubes and amorphous carbon, and Li2NiO2 provides Li as a lithium supplement agent. + .

[0099] Example 5

[0100] The difference from Example 1 is that the carbon nanotubes obtained have a tube diameter in the range of 9nm-11nm and a length in the range of 20μm-30μm.

[0101] Example 6

[0102] The difference from Example 1 is that the content of benzene in Example 1 is fine-tuned so that the mass percentage of the shell layer in the composite lithium supplement material is 3.5%.

[0103] Example 7

[0104] The difference from Example 1 is that the content of benzene in Example 1 is fine-tuned so that the average thickness of the shell layer is 10nm.

[0105] Example 8

[0106] The difference from Example 1 is that the inner core surface has a three-dimensional conductive network.

[0107] Comparative Example 1

[0108] (1) Mix LiNO3 and Fe2O3 in a molar ratio of 5:1, stir uniformly, and then sinter at 850°C for 8h under a nitrogen atmosphere, crush, sieve, and obtain a lithium supplement source-Li5FeO4.

[0109] (2) Dissolve polyaniline in nitrogen pyrrolidone, mix with lithium supplement source-Li5FeO4 uniformly, place in a reaction kettle, react for 1 h at 250°C under nitrogen atmosphere, and vacuum dry to obtain a composite lithium supplement material.

[0110] The shell of the composite lithium supplement material is composed of amorphous carbon only, the average thickness of the shell is 7 nm, the average particle size of the core is 30 μm, and the mass percentage of the shell is 0.95%.

[0111] Comparative Example 2

[0112] (1) Mechanically crush Li2CO3 and anion source-CS2 in a molar ratio of 2:1, mix uniformly, sinter at 780°C for 10 h under nitrogen atmosphere, crush, sieve, and obtain lithium supplement source-Li2S.

[0113] (2) Mix toluene with lithium supplement source-Li2S uniformly, place in a muffle furnace, sinter at 600°C for 1.5 h under nitrogen atmosphere, and obtain a composite lithium supplement material.

[0114] The shell of the composite lithium supplement material is composed of amorphous carbon only, the average thickness of the shell is 10 nm, the average particle size of the core is 20 μm, and the mass percentage of the shell is 0.83%.

[0115] Comparative Example 3

[0116] (1) Mechanically crush LiOH and Ni(OH)2 in a molar ratio of 2:1, mix uniformly, sinter at 900°C for 6 h under nitrogen atmosphere, crush, sieve, and obtain lithium supplement source-Li2NiO2.

[0117] (2) Mix acetone with lithium supplement source-Li2NiO2 uniformly, place in a reaction kettle, react for 2 h at 300°C under nitrogen atmosphere, and vacuum dry to obtain a composite lithium supplement material.

[0118] The shell of the composite lithium supplement material is composed of amorphous carbon only, the average thickness of the shell is 8 nm, the average particle size of the core is 25 μm, and the mass percentage of the shell is 1.02%.

[0119] Comparative Example 4

[0120] (1) Mechanically crush Li2CO3 and Fe(OH)3 in a molar ratio of 2.5:1, mix uniformly, sinter at 700°C for 10 h under nitrogen atmosphere, crush, sieve, and obtain lithium supplement source-Li5FeO4.

[0121] (2) The lithium supplement source Li5FeO4 and the doping source Al(NO3)3 were mixed in a ratio of 1:1 and placed in a reaction kettle. After reaction at 300°C for 2h under a nitrogen atmosphere, vacuum drying, and mixing with crushed polypropylene waste plastics, the mixture was placed in a box furnace and reacted at 600°C for 1h under a nitrogen atmosphere to obtain the composite lithium supplement material.

[0122] At this time, the Fe element cannot catalyze the growth of carbon nanotubes together with Al as a catalyst, so that the shell layer of the composite lithium supplement material is composed of amorphous carbon only and does not contain carbon nanotubes. The average thickness of the shell layer is 3nm, and the average particle size of the core is 15μm. The mass percentage of the shell layer is 0.92%.

[0123] The composite lithium supplement materials prepared in the examples and comparative examples of the present application were subjected to the following tests:

[0124] (1) Morphology characterization: the composite lithium supplement material prepared in Example 1 was subjected to SEM testing to observe its surface morphology.

[0125] (2) Gravimetric capacity test: the composite lithium supplement materials prepared in the above examples and comparative examples were respectively prepared into positive electrodes and assembled into lithium ion batteries according to the following methods:

[0126] Positive electrode sheet: the composite lithium supplement material was mixed with lithium cobaltate in a certain mass ratio to obtain a target material. The target material was mixed with a conductive agent-super-P and a binder-PVDF in a mass ratio of 95:2:3, and ball-milled and stirred for 60min at a rotation speed of 30HZ. After homogenization-coating-drying-sheet cutting, positive electrode sheets were respectively prepared. The positive electrode sheets were baked in a vacuum oven at 100°C to remove trace water;

[0127] Negative electrode sheet: a lithium metal sheet with a diameter of 16mm was prepared.

[0128] The prepared negative electrode sheet, separator, and positive electrode sheet were alternately stacked to obtain a dry cell. The positive and negative electrode sheets were alternately separated by the separator. The dry cell was placed in an aluminum plastic film outer package, injected with electrolyte, and then vacuum sealed. After standing at 60°C for 48h, pressure layering, secondary packaging, degassing, and capacity distribution were performed to obtain the composite lithium supplement material-lithium ion battery. The electrolyte composition was: 1mol / L LiPF6 solution, and the solvent was composed of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1. The separator was a polypropylene microporous separator.

[0129] The composite lithium supplement material-lithium ion batteries prepared above were tested for the first charge-discharge specific capacity according to the following method:

[0130] 0.05C charged to 4.5V, 4.5V constant voltage to current less than 0.01C; 0.05C discharged to 2.5V, test its first charge-discharge specific capacity. The results are summarized in Table 1.

[0131] (3) The composite lithium supplement material prepared in each of the above examples and comparative examples is added to the positive electrode active material to prepare a secondary battery.

[0132] a) Preparation of positive electrode sheet: The composite lithium supplement material prepared in each of the above examples and comparative examples is mixed with the positive electrode active material lithium iron phosphate to obtain a positive electrode composite material. The positive electrode composite material, the binder PVDF and the conductive agent super-p are uniformly mixed and dissolved in water to obtain a positive electrode slurry. The mass ratio of the composite lithium supplement material to the positive electrode active material lithium iron phosphate is 2:98, and the mass ratio of the positive electrode composite material, the binder and the conductive agent is 95:2:3. The obtained positive electrode slurry is coated on the positive electrode current collector aluminum foil, and then dried, die-cut to obtain the positive electrode sheet.

[0133] b) Preparation of negative electrode sheet: 100 g of graphite negative electrode active material is added to water, and the mixture is uniformly mixed to obtain a negative electrode slurry. The above negative electrode slurry is uniformly coated on the surface of the negative electrode current collector copper foil. After drying, the sheet is pressed by a roller press to obtain the negative electrode sheet. Thus, the negative electrode sheet is obtained.

[0134] c) Preparation of secondary battery: The positive electrode sheet, the negative electrode sheet and the separator obtained by the above steps are alternately stacked together to prepare a battery by the lamination method, wherein the positive and negative electrode sheets are arranged alternately, and the adjacent positive and negative electrode sheets are separated by the separator to obtain a dry cell. The dry cell is placed in an aluminum plastic film outer package, electrolyte is injected, and then vacuum sealed. After standing at 60°C for 48h, the full battery is obtained by pressure layering, secondary packaging, degassing and capacity distribution at 60°C.

[0135] Among them, the batteries with the positive electrode sheets provided with the composite lithium supplement materials of Examples 1-8 are respectively marked as S1-S8, and the batteries with the positive electrode sheets provided with the composite lithium supplement materials of the comparative examples are respectively marked as DS1-DS4.

[0136] The above batteries are subjected to electrochemical performance test, and are respectively charged at 0.05C to 4.3V, and 4.3V constant voltage to current less than 0.01C. The first charge capacity of the battery and the cycle capacity retention rate after 100 cycles of the battery are tested. The results are summarized in Table 2.

[0137] Table 1: Carbon content and capacity test results of the composite lithium supplement materials prepared in each of the examples and comparative examples

[0138]

[0139] Table 2: Electrochemical performance test results of batteries prepared from each example and comparative example

[0140]

[0141]

[0142] The SEM image of the composite lithium supplementing material prepared from Example 1 (see Figure 2A and Figure 2B ) can be clearly seen that the composite lithium supplementing material has carbon nanotubes, and part of the carbon nanotubes are wrapped on the surface of the composite lithium supplementing material, and there are also some carbon nanotubes extending from the inside of the composite lithium supplementing material.

[0143] In addition, as can be seen from the data in Table 1, under the condition that the material composition is the same, the 25% humidity placement 0h gram capacity of the composite lithium supplementing material provided by the examples is slightly better than that of the comparative examples, but the environmental stability of the composite lithium supplementing material provided by all the examples is significantly better than that of the comparative examples. And the first charge gram capacity and the battery capacity retention rate after 100 cycles of the secondary battery with the composite lithium supplementing material provided by the examples are significantly better than those of the comparative battery.

[0144] The above is an exemplary embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, some improvements and refinements can also be made, these improvements and refinements are also considered within the scope of protection of the present application.

Claims

1. A composite lithium supplementation material, characterized in that, The composite lithium replenishing material is applied to the positive electrode of a battery. It comprises a core and a shell grown in situ on the surface of the core. The core includes a doped lithium replenishing agent, and the shell comprises amorphous carbon and carbon nanotubes dispersed in the amorphous carbon, with at least a portion of the carbon nanotubes in contact with the core. The doped lithium replenishing agent contains a transition metal element, which catalyzes the in-situ generation of carbon nanotubes and precipitation of amorphous carbon on the surface of the doped lithium replenishing agent by carbon atoms in an organic carbon source. At least a portion of the carbon nanotubes extend from the core towards the shell. The mass percentage of the carbon nanotubes in the shell is in the range of 0.1%-10%.

2. The composite lithium replenishment material according to claim 1, characterized in that, At least a portion of the carbon nanotubes form a three-dimensional conductive network on the surface of the core.

3. The composite lithium replenishment material according to claim 1, characterized in that, The diameter of the carbon nanotubes is in the range of 5nm-100nm.

4. The composite lithium replenishment material according to claim 1, characterized in that, The length of the carbon nanotubes is in the range of 3μm-50μm.

5. The composite lithium replenishment material according to claim 1, characterized in that, The transition metal element includes at least one of Fe, Co, Ni, Mn, Mo, and Cu.

6. The composite lithium replenishment material according to claim 1, characterized in that, In the doped lithium replenishing agent, the doping element includes at least one of Fe, Co, Ni, Mn, Mo and Cu.

7. The composite lithium replenishment material according to claim 6, characterized in that, In the doped lithium replenisher, the molar percentage of the doped element in the core is in the range of 1%-50%.

8. The composite lithium replenishment material according to claim 1, characterized in that, The doping element includes a second element, which includes Al and / or Mg.

9. The composite lithium replenishment material according to claim 1, characterized in that, The shell layer comprises 1.0%-5.5% by mass in the composite lithium replenishment material.

10. The composite lithium supplementation material according to claim 1, characterized in that, The diameter of the core is in the range of 0.05μm-100μm, and the average thickness of the shell is in the range of 3nm-100nm.

11. The composite lithium supplementation material according to any one of claims 1-10, characterized in that, The specific capacity of the composite lithium replenishment material stored for 24 hours at an ambient humidity of 25% decreases by no more than 25% compared to the specific capacity stored for 0 hours.

12. A method for preparing a composite lithium supplement material, characterized in that, Includes the following steps: (1) Prepare a doped lithium replenishing agent precursor by mixing the lithium replenishing agent source with the doping source; (2) The doped lithium supplement precursor is mixed with an organic carbon source and calcined under an inert atmosphere to grow carbon nanotubes and amorphous carbon to obtain a composite lithium supplement material. The composite lithium replenishing material is used in the positive electrode of a battery. The composite lithium replenishing material includes a core and a shell. The core includes a doped lithium replenishing agent, and the shell includes amorphous carbon and carbon nanotubes dispersed in the amorphous carbon, with at least a portion of the carbon nanotubes in contact with the core. The doped lithium replenishing agent contains a transition metal element, which catalyzes the in-situ generation of carbon nanotubes and precipitation of amorphous carbon on the surface of the doped lithium replenishing agent by carbon atoms in an organic carbon source. At least a portion of the carbon nanotubes extend from the core towards the shell. The mass percentage of carbon nanotubes in the shell is in the range of 0.1%-10%.

13. A positive electrode composite material, characterized in that, The positive electrode composite material includes the composite lithium replenishing material as described in any one of claims 1-11 or the composite lithium replenishing material prepared by the preparation method described in claim 12.

14. A positive electrode plate, characterized in that, The positive electrode sheet has the positive electrode composite material as described in claim 13.

15. A battery, characterized in that, The battery has a positive electrode as described in claim 14.

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